Tran Ian, Ji Changhoon, Ni Inzer, Min Taehong, Tang Danni, Vij Neeraj
Departments of 1 Pediatric Respiratory Science and.
2 Biomedical Engineering, the Johns Hopkins University School of Medicine, Baltimore, Maryland; and.
Am J Respir Cell Mol Biol. 2015 Aug;53(2):159-73. doi: 10.1165/rcmb.2014-0107OC.
Cigarette smoke (CS) exposure is known to induce proteostasis imbalance that can initiate accumulation of ubiquitinated proteins. Therefore, the primary goal of this study was to determine if first- and secondhand CS induces localization of ubiquitinated proteins in perinuclear spaces as aggresome bodies. Furthermore, we sought to determine the mechanism by which smoke-induced aggresome formation contributes to chronic obstructive pulmonary disease (COPD)-emphysema pathogenesis. Hence, Beas2b cells were treated with CS extract (CSE) for in vitro experimental analysis of CS-induced aggresome formation by immunoblotting, microscopy, and reporter assays, whereas chronic CS-exposed murine model and human COPD-emphysema lung tissues were used for validation. In preliminary analysis, we observed a significant (P < 0.01) increase in ubiquitinated protein aggregation in the insoluble protein fraction of CSE-treated Beas2b cells. We verified that CS-induced ubiquitin aggregrates are localized in the perinuclear spaces as aggresome bodies. These CS-induced aggresomes (P < 0.001) colocalize with autophagy protein microtubule-associated protein 1 light chain-3B(+) autophagy bodies, whereas U.S. Food and Drug Administration-approved autophagy-inducing drug (carbamazepine) significantly (P < 0.01) decreases their colocalization and expression, suggesting CS-impaired autophagy. Moreover, CSE treatment significantly increases valosin-containing protein-p62 protein-protein interaction (P < 0.0005) and p62 expression (aberrant autophagy marker; P < 0.0001), verifying CS-impaired autophagy as an aggresome formation mechanism. We also found that inhibiting protein synthesis by cycloheximide does not deplete CS-induced ubiquitinated protein aggregates, suggesting the role of CS-induced protein synthesis in aggresome formation. Next, we used an emphysema murine model to verify that chronic CS significantly (P < 0.0005) induces aggresome formation. Moreover, we observed that autophagy induction by carbamazepine inhibits CS-induced aggresome formation and alveolar space enlargement (P < 0.001), confirming involvement of aggresome bodies in COPD-emphysema pathogenesis. Finally, significantly higher p62 accumulation in smokers and severe COPD-emphysema lungs (Global Initiative for Chronic Obstructive Lung Disease Stage III/IV) as compared with normal nonsmokers (Global Initiative for Chronic Obstructive Lung Disease Stage 0) substantiates the pathogenic role of autophagy impairment in aggresome formation and COPD-emphysema progression. In conclusion, CS-induced aggresome formation is a novel mechanism involved in COPD-emphysema pathogenesis.
已知接触香烟烟雾(CS)会导致蛋白质稳态失衡,进而引发泛素化蛋白的积累。因此,本研究的主要目的是确定一手和二手CS是否会诱导泛素化蛋白在核周空间中定位形成聚集体。此外,我们试图确定烟雾诱导聚集体形成导致慢性阻塞性肺疾病(COPD)-肺气肿发病机制的机制。因此,使用CS提取物(CSE)处理Beas2b细胞,通过免疫印迹、显微镜检查和报告基因检测对CS诱导的聚集体形成进行体外实验分析,而慢性CS暴露小鼠模型和人类COPD-肺气肿肺组织则用于验证。在初步分析中,我们观察到CSE处理的Beas2b细胞不溶性蛋白部分中泛素化蛋白聚集显著增加(P < 0.01)。我们证实CS诱导的泛素聚集体作为聚集体位于核周空间。这些CS诱导的聚集体(P < 0.001)与自噬蛋白微管相关蛋白1轻链3B(+)自噬体共定位,而美国食品药品监督管理局批准的自噬诱导药物(卡马西平)显著(P < 0.01)降低它们的共定位和表达,提示CS损害自噬。此外,CSE处理显著增加含缬酪肽蛋白-p62蛋白-蛋白相互作用(P < 0.0005)和p62表达(异常自噬标志物;P < 0.0001),证实CS损害自噬是聚集体形成机制。我们还发现用环己酰亚胺抑制蛋白质合成不会消耗CS诱导的泛素化蛋白聚集体,提示CS诱导的蛋白质合成在聚集体形成中的作用。接下来,我们使用肺气肿小鼠模型验证慢性CS显著(P < 0.0005)诱导聚集体形成。此外,我们观察到卡马西平诱导的自噬抑制CS诱导的聚集体形成和肺泡腔扩大(P < 0.001),证实聚集体在COPD-肺气肿发病机制中的作用。最后,与正常非吸烟者(慢性阻塞性肺疾病全球倡议0期)相比,吸烟者和重度COPD-肺气肿患者(慢性阻塞性肺疾病全球倡议III/IV期)肺组织中p62积累显著更高,证实自噬受损在聚集体形成和COPD-肺气肿进展中的致病作用。总之,CS诱导的聚集体形成是COPD-肺气肿发病机制中的一种新机制。